Talks

Macroecology, as a relatively new field in Ecology, holds distinct methodological characteristics that lead to profound philosophical changes in the nature of evidence to support and build theories and models. One reason for this is the impracticability of controlled or manipulative experimental studies at broad spatial and temporal scales, as well as historical contingencies and the complexity of ecological dynamics at these scales. We follow here a model-based reasoning for building scientific theories and show in particular how computer simulation models, applied to different case studies in diversity gradients, can be successfully used in macroecology as mediating theory and data.  

String theory suggests the existence of multiple axion species forming what is known as an “axiverse”. The axions in this model are thought to have logarithmically-distributed masses extending far below 10^{-21} eV, leading to the presence of ultralight axions. The latter have astrophysical de Broglie wavelength and affect the cosmic structures in which they cluster by erasing small-scale features. In contrast to other ultralight or fuzzy dark matter models, the string axiverse allows for a mixed dark sector with a subdominant ultralight component. Trace amounts of ultralight axions have been shown alleviate some observational discrepancies in cosmology such as the missing satellite problem and the Hubble-S8 tensions. Using an effective field theory approach and data from the Baryon Oscillation Spectroscopic Survey, we reach the strongest constraints on the axion relic density for axions with masses below 10^{-25} eV. To study heavier axions, we develop a new algorithm capable of simulating the formation of large-scale structure in the presence of more than one axion species. Making use of this code, we isolate new observational features in the cosmic web which may help us detect the presence of a plenitude of axions with weak lensing surveys.

Zoom Link: https://pitp.zoom.us/j/95089179013?pwd=NTBIeitScFRhYnBBSnlrcnoyVEhydz09